Method of geothermal loop installation

ABSTRACT

According to one aspect of the invention, there is provided a method for drilling a hole into the ground and installing a geothermal transfer loop. A drilling apparatus is positioned at a desired location. The drilling apparatus includes a rotating and vibrating apparatus, such as a sonic drill, for rotating and vibrating a hollow drill string into the ground. The hollow drill string having an inner space. A hole is drilled to a desired depth by rotating and vibrating the hollow drill string into the ground and discharging fluid into the inner space of the hollow drill string. A geothermal transfer loop is lowered into the inner space of the hollow drill string and the drill string is removed from the ground. The method may also include discharging grouting material into the hole.

BACKGROUND OF THE INVENTION

This invention relates to the geothermal heat exchange systems, and inparticular, to the installation of geothermal transfer loops with sonicdrills.

Geothermal heat exchange systems are environmentally friendly, energyefficient heating and cooling systems. As such, there is a rising demandfor geothermal heat exchange systems for both commercial and residentialproperties. There is therefore a need for a quick and efficient methodof installing the geothermal transfer loops used in many geothermal heatexchange systems.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a method fordrilling a hole and installing a geothermal transfer loop. A drillingapparatus is positioned at a desired location. The drilling apparatusincludes a rotating and vibrating apparatus for rotating and vibrating ahollow drill string into the ground. The hollow drill string having aninner space. A hole is drilled to a desired depth by rotating andvibrating the hollow drill string into the ground while dischargingfluid into the inner space of the hollow drill string. A geothermaltransfer loop is lowered into the inner space of the hollow drill stringand the drill string is removed from the ground. The method may alsoinclude discharging grouting material into the hole.

According to another aspect of the invention, there is provided a methodof drilling a hole and installing a geothermal transfer loop. A drillingapparatus is positioned at a desired location. The drilling apparatusincludes a rotating and vibrating apparatus for rotating and vibrating ahollow drill string into the ground. The hollow drill string having aninner space. A hole is drilled to a desired depth by rotating andvibrating the hollow drill string into the ground while discharging afluid into the inner space of the hollow drill string. A geothermaltransfer loop is lowered into the inner space of the hollow drillstring. The geothermal transfer loop is filled with a second fluid and aportion of the geothermal transfer loop is straight. The straightenedportion of the geothermal transfer loop is lowered first. Weights areattached to the geothermal transfer loop. The hollow drill string isvibrated out of the ground while grouting material is simultaneouslydischarged into the inner space of the hollow drill string. Thegeothermal transfer loop is operatively connected to a heat exchanger.

This invention provides the advantages of being able to drill casedholes faster and in litholgies that are often difficult for conventionaldrill rigs to drill in. This invention also provides the furtheradvantage of being able to more accurately control and monitor thegrouting process.

This invention provides the further advantage of being able to lower thegeothermal transfer loop supplied in coils by eliminating the problem ofthe coils catching on mud on the side of the hole because the hole iscased.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Drawings:

FIG. 1 is an elevational, partly in section view of a drilling rigdrilling a hole, using a method according to the invention;

FIG. 2 is an elevational, cross-sectional diagram illustratingpressurized fluid carrying drill cuttings to the ground surface, using amethod according to the invention;

FIG. 3 is an elevational, cross-sectional diagram illustrating thelowering of a geothermal transfer loop into the hole, using a methodaccording to the invention;

FIG. 4 is an elevational, cross-sectional view of a rig grouting thehole, using a method according to the invention; and

FIG. 5 is an elevational view of a geothermal exchange loop connected toa heat exchanger, using a method according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, and first to FIG. 1, this shows a method ofdrilling a hole 12 into the ground 14 according to a preferred method ofthe invention. A drilling apparatus 20 is mounted on a movable vehicle50. The vehicle 50 is moved to a desired drilling location and thedrilling apparatus 20 is placed in a desired drilling position. A drillpipe 22 is threadedly connected to the drilling apparatus 20 at a firstend 23, and the drill pipe 22 is threadedly connected to a drill bit 28at a second end 24. The drill pipe 22 is hollow and is open at both ends23 and 24. In this example, the drill bit 28 is a ring bit that isconcentric with drill pipe 22. This combination of drill pipe 22 anddrill bit 28 forms an open ended drill string 30. There is a cavity orinner space 35 encompassed by the drill string 30.

The drilling apparatus 20 is a rotary and vibratory apparatus such as asonic drill. Sonic drills are known in the art and accordingly are notdescribed in more detail herein. Examples of sonic drills are describedin my earlier U.S. Pat. No. 5,027,908 and U.S. Pat. No. 5,409,070 whichare hereby incorporated by reference. The drilling apparatus rotates andvibrates the drill string 30 into the ground 14. A hose 42 hydraulicallyconnects a pressurized fluid pump apparatus 40 to the drillingapparatus. A pressurized fluid is pumped by the pressurized fluidapparatus or pump 40 along the hose 42, through the drilling apparatus20, and into the inner space 35 of the drill string 30 as indicated byarrow 44 during the drilling process. In this example of the method, thepressurized fluid is water but water with added components such aspolymer or clay may also be used. The fluid has a pressure range ofbetween 10-5000 psi, with the preferred pressure range being between500-2000 psi. This pressure facilitates faster drilling in groundconditions that would otherwise block the flow of pressurized fluid outof the drill bit 28.

A column of fluid 37 fills the inner space 35 acting as a plug in thedrill string 30, impeding the entry of ground materials into the innerspace 35. The diameter of the hose 42 is less than the diameter of theinner space 35, thereby preventing the pressurized fluid from beingpushed back through the hose in response to high pressure spikes createdwhen the pressurized fluid impacts the ground 14 in the hole 12. Thevibrating drill string 30 causes the pressure in the fluid column tooscillate at the same frequency that the drill string is vibrated at.The pressure spikes thus created causes the fluid column to act in amanner similar to a water hammer, thereby adding an additional drillingforce.

At minimum, sufficient pressurized fluid is pumped into the inner space35 to form a fluid column 37 that impedes the entry of ground materialsinto the inner space 35. However, additional pressurized fluid may bepumped into the inner space 35 in order to carry cuttings up the annulus13, between the drill string and the hole, to the ground surface 15, asillustrated in FIG. 2. Arrow 44 indicates the direction of the flow ofpressurized fluid into the ground 14 through the inner space 35 of thedrill string 30. The excess pressurized fluid is pushed down and aroundthe drill bit 28 and up the annulus 13 towards the surface as indicatedby arrows 45 and 46. The pressurized fluid carries cuttings as it movesup the annulus 13 to the ground surface 15 where the pressurized fluidand cuttings are expelled from the hole 12 as indicated by arrows 47 and48.

As the depth of the hole increases, additional drill pipes (not shown)may be added to the drill string 30 in sequence. Each additional drillpipe has a first end and a second end. The additional drill pipes arehollow and open at both ends. The first ends of the additional drillpipes are threadedly connected to the drilling apparatus 20 and thesecond ends of the additional drill pipes are threadedly connected tothe drill string 30. The additional drill pipes may then be rotated andvibrated into the ground, thereby increasing the length of the drillstring 30 and the depth of the hole 12. The additional drill pipes maybe added manually or with an automated drill pipe handling apparatus.Once the hole 12 has been drilled to a desired depth the drill string 30is disconnected from the drilling apparatus 20, leaving a hole 12 whichis cased by the drill string 30, as illustrated in FIG. 3. A geothermaltransfer loop 70 is lowered into the hole 12 through the inner space 35of the drill string 30, as indicated by arrow 44. It is to be notedhowever, that in other examples of the method the drill string 30 may beremoved prior to the lowering of the geothermal transfer loop 70 intothe hole 12.

The geothermal transfer loop is preferably filled with a fluid prior tobeing lowered into the hole 12. In this example of the method, thegeothermal transfer loop 70 is a high density polyethylene tube and isfilled with water. The fluid adds weight to the geothermal transfer loop70 and prevents the geothermal transfer loop 70 from collapsing in anyfluid column that may remain in the inner space 35 of the drill string30. Weights 75 may also be attached to the geothermal transfer loop 70to facilitate the lowering of the geothermal transfer loop 70 into thehole 12. The lead portion 71 of the geothermal transfer loop 70 may bestraightened to aid in keeping the geothermal transfer loop 70 at thebottom of the hole 12 during grouting and withdrawal of the drill string30. In this example of the method, the weight 75 is an elongated pieceof steel bar that has been attached to the lead portion 71 of thegeothermal transfer loop 70 by wiring 76 around the steel bar and thegeothermal transfer loop. The steel bar performs the dual function of aweight and a means for straightening the lead portion 71 of thegeothermal transfer loop 70. Once the geothermal loop 70 has beencompletely lowered the drill string is removed from the hole 12 and thehole is grouted. The hole 12 may be grouted with the drill string 30remaining in the ground 14 or after the drill string 30 has been removedfrom the ground.

In this example of the method, grouting is accomplished by the tremieline method as illustrated in FIG. 4. A tremie line hose 80 is loweredinto the hole 12. The tremie line hose is comprised of a steel pipesection 82 at a first end and a flexible tube section 81 at a secondend, the steel pipe section 82 being the lead end of the tremie line 80lowered into the hole 12. A pump 86 pumps thermally conductive groutingmaterial 120 from a reservoir 88 along the tremie hose line 80 to thebottom of the hole 12. The grouting material 120 encompasses thegeothermal transfer loop 70. As the hole 12 is filled from the bottomup, a tremie line hose reel 87 pulls the tremie line hose 80 out of thehole 12, so as to maintain the lead end of the of the tremie line hose80 below the grouting material 120. This process is continued until thehole 12 has been filled with grouting material 120 and the groutingmaterial encompasses the portion of the geothermal transfer loop 70which is below the ground surface 15.

In other examples of the method, grouting may be accomplished by thepressure grouting method. Pressure grouting may be accomplished byattaching a grout line to the top of the of the drill string 30 or agrout line can be attached to the swivel on the drill head. As the drillstring 30 is removed from the ground, grouting material issimultanoeusly pumped into the inner space 35 of the drill string 30.The grouting is topped up once the casing has been removed. In somecases grouting may not be required, for example in silty or sandy soilswhich collapse about the geothermal loop when the drill string isremoved.

Once the grouting process is completed, either by the tremie line methodor the pressure grouting method, the geothermal transfer loop 70 may beoperatively connected to a heat exchanger 100, as illustrated in FIG. 5.The geothermal transfer loop 70 may also be operatively connected belowthe ground surface, in series, to additional geothermal transfer loopsbelow the surface. The series geothermal transfer loops are thenconnected to a communal heat exchanger.

It will be understood by someone skilled in the art that many of thedetails provided above are by way of example only and can be varied ordeleted without departing from the scope of the invention as set out inthe following claims.

1. A method of drilling a hole into the ground and installing ageothermal transfer loop, the method comprising: positioning a drillingapparatus at a desired location, the drilling apparatus including arotating and vibrating apparatus for rotating and vibrating a hollowdrill string into the ground, the hollow drill string having an innerspace; drilling the hole to a desired depth by rotating and vibratingthe hollow drill string into the ground and discharging a first fluidinto the inner space of the hollow drill string; lowering the geothermaltransfer loop into the inner space of the hollow drill string followingthe drilling of the hole to the desired depth; and removing the hollowdrill string from the ground.
 2. The method claimed in claim 1, furtherincluding discharging grouting material into the hole following thelowering of the geothermal transfer loop into the inner space of thehollow drill string.
 3. The method claimed in claim 1, further includingvibrating the hollow drill string out of the ground while simultaneouslydischarging grouting material into the inner space of the hollow drillstring following the lowering of the geothermal transfer loop into theinner space of the hollow drill string.
 4. The method claimed in claim1, further including filling the geothermal transfer loop with a secondfluid prior to lowering the geothermal transfer loop into the innerspace of the hollow drill string.
 5. The method claimed in claim 1,further including attaching a weight to the geothermal transfer loopprior to lowering the geothermal transfer loop into the inner space ofthe hollow drill string.
 6. The method claimed in claim 1, furtherincluding straightening a portion of the geothermal transfer loop andcausing a straightened portion of the geothermal loop to be loweredfirst.
 7. The method claimed in claim 1, further including operativelyconnecting the geothermal transfer loop to a heat exchanger.
 8. Themethod claimed in claim 1, wherein the hollow drill string is comprisedof a drill pipe and drill bit, the drill bit being a ring bit,sufficient first fluid being discharged into the inner space of thehollow drill string so as to keep the inner space clear of debris. 9.The method claimed in claim 1, wherein the hollow drill string iscomprised of a drill pipe and drill bit, the drill bit being a ring bit,sufficient first fluid being discharged into the inner space of thehollow drill string so as to carry debris up an outside of the hollowdrill string to the ground surface or to push the debris into theground.
 10. A method of drilling a hole and installing a geothermaltransfer loop, the method comprising: positioning a drilling apparatusat a desired location, the drilling apparatus comprising a rotating andvibrating apparatus for rotating and vibrating a hollow drill stringinto a ground, the hollow drill string having an inner space; drillingthe hole to a desired depth by rotating and vibrating the hollow drillstring into the ground and discharging a first fluid into the innerspace of the hollow drill string; straightening a portion of thegeothermal transfer loop; lowering the geothermal transfer loop into theinner space of the hollow drill string following the drilling of thehole to the desired depth, the geothermal transfer loop being filledwith a second fluid, the straightened portion of the geothermal transferloop being lowered first, weights being attached to the geothermaltransfer loop; vibrating the hollow drill string out of the ground whilesimultaneously discharging grouting material into the inner space of thehollow drill string; and operatively connecting the geothermal transferloop to a heat exchanger.
 11. A method of drilling a hole and installinga geothermal transfer loop, the method comprising: positioning adrilling apparatus at a desired location, the drilling apparatuscomprising a rotating and vibrating apparatus for rotating and vibratinga hollow drill string into the ground, the hollow drill string having aninner space; drilling the hole to a desired depth by rotating andvibrating the hollow drill string into the ground and discharging afluid into the inner space of the hollow drill string; lowering thegeothermal transfer loop into the inner space of the hollow drill stringfollowing the drilling of the hole to the desired depth; discharginggrouting material into the inner space of the hollow drill string; andoperatively connecting the geothermal transfer loop to a heat exchanger.12. A system for drilling a hole and installing a geothermal transferloop, the system comprising: a drilling apparatus including a rotatingand vibrating apparatus for rotating and vibrating a hollow drill stringinto the ground, the hollow drill string having an inner space; a fluiddischarging apparatus for discharging a fluid into the inner space ofthe hollow drill string; a geothermal transfer loop for lowering intothe inner space of the hollow drill string; and a grouting apparatus fordischarging grouting material to encompass the geothermal transfer loop.13. The system claimed in claim 12, wherein the fluid dischargingapparatus and the drilling apparatus operate simultaneously.
 14. Thesystem as claimed in claim 12, wherein a hose connects the fluiddischarging apparatus to the drilling apparatus.
 15. The system asclaimed in claim 14, wherein the hose has a cross-sectional area and theinner space of the hollow drill string has a cross sectional area, thecross-sectional area of the hose being less than the cross sectionalarea of the inner space of the hollow drill string.
 16. The system asclaimed in claim 12, wherein the grouting apparatus and the drillingapparatus operate simultaneously.
 17. The system as claimed in claim 12,wherein the hollow drill string includes a drill pipe and a drill bit.18. The system as claimed in claim 12, wherein the drill pipe has afirst end and a second end, the drill pipe being hollow and the drillpipe being open at the first end and open at the second end.
 19. Thesystem as claimed in claim 17, wherein the drill bit is a ring bit. 20.The system as claimed in claim 17, wherein the drill bit is concentricwith the drill pipe.